Field of the Invention
The invention relates to a method for regulating a volumetric fuel flow delivered by a feed pump to a high-pressure pump connected to a high-pressure reservoir. The invention also relates to an apparatus for regulating the volumetric fuel flow delivered by a feed pump to a high-pressure pump.
Regulating a volumetric fuel flow in an inflow to a high-pressure pump, which pumps fuel into a high-pressure reservoir of a common rail injection system of an internal combustion engine, requires optimized adaptation, since on one hand it must be assured that the high-pressure pump is supplied with enough fuel to suit the engine operating conditions, and on the other hand, the high-pressure pump should nevertheless not pump excess fuel into the high-pressure reservoir, since the excess fuel is returned to the engine tank through a high-pressure valve and thus causes warming of the fuel in the tank. In addition, fuel is highly compressed unnecessarily by the high-pressure pump as a result, which represents an unnecessary power loss.
Published European Patent Application 0 299 337 A2 describes a method and an apparatus for regulating the volumetric fuel flow that is supplied by a feed pump to a high-pressure pump. A regulatable throttle that is triggered by a control unit is disposed between the feed pump and the high-pressure pump. An arithmetic unit monitors the fuel pressure in the high-pressure reservoir and controls the regulatable throttle in accordance with the fuel demand of the engine and the fuel pressure in the high-pressure reservoir.
Regulating the fuel pressure in the high-pressure reservoir is relatively complicated. In that method both the fuel pressure and the expected consumption by the engine must be ascertained and an opening cross section of the regulatable throttle must be calculated by the arithmetic unit from those variables.